The capacitor for use in electronic devices such as cellular phone and personal computer is demanded to have a large capacitance with a small size. Among these capacitors, a tantalum solid electrolytic capacitor has a large capacitance for the size and also has good performance and therefore, this is being preferably used. Other than the tantalum solid electrolytic capacitor, a niobium solid electrolytic capacitor using niobium, which is an inexpensive material, for the anode is recently studied. In producing such a solid electrolytic capacitor, a capacitor element comprising a dielectric layer formed on an anode surface by electrochemical formation, a semiconductor layer sequentially stacked on the dielectric layer, and an electrically conducting layer formed on the semiconductor layer is connected to an external terminal and then jacketed to complete the solid electrolytic capacitor. The produced solid electrolytic capacitor is mounted together with other electronic parts on a circuit board or the like and used in practice, but in some cases, the leakage current (hereinafter, simply referred to as “LC”) value of the capacitor increases due to heat of soldering at the mounting.
In order to solve this problem, for example, a method of leaving the semiconductor layer to stand at a temperature higher than the curing temperature of jacketing resin and thereby preventing the increase of LC has been proposed in JP-A-6-310382 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”).